Petroleum crude oils contain many impurities such as organic acids and asphaltenes. Amongst the organic acids, naphthenic acids are one of the major impurities. Naphthenic acids are highly corrosive and corrode the refining process equipment. Generally, naphthenic acid causes severe corrosion at high temperature i.e., 200 to 400° C. Moreover, due to the presence of polar carboxylic acid groups, low molecular weight naphthenic acids act as surfactants and during the desalting process they create problems by forming tight water-in-oil emulsion.
Due to the above mentioned processing problems, naphthenic acid removal from crude oil is necessary. There are several methods available for removing acidic components from crude oil including neutralization using oxides or hydroxides of alkali or alkaline earth metals or amine compounds, treatment with zeolites, esterification with alcohols, use of ion-exchange method and the like.
Although neutralization or esterification methods are simple to execute, they lead to conversion of the acidic portion into metal salts which create problem in the downstream process unit.
However, no harmful byproduct is evolved in ion-exchange method. Therefore, it is a widely used method for the de-acidification of crude oil.
The ion-exchange resin after it has been spent, due to the saturation of acids, needs to be regenerated for restoring the ion-exchange capability.
U.S. Pat. No. 4,037,656 discloses a method for removing carboxylic acids from the carboxylic acid containing ion-exchange resin. In the method, carboxylic acid containing ion-exchange resin is contacted with an alcoholic caustic solution to remove carboxylic acid.
However, this method is not satisfactory because it does not remove carboxylic acids efficiently and hence is incapable of regenerating the ion-exchange resin completely. In view of this, there exists a need for a simple and efficient method for regeneration of deactivated resins to restore their ion exchange capacity.